Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Dec. 31, 2014	$ 863,465	$ 489	$ 220,982	$ 649,174	$ (7,180)
Balance (in shares) at Dec. 31, 2014		48,966
Increase (Decrease) in Stockholders' Equity
Net income	31,560			31,560
Translation adjustment, net of tax	(8,702)				(8,702)
Options exercised	5,576	$ 2	5,574
Stock options exercised (in shares)		190
Stock-based compensation	5,995		5,995
Tax benefit of options exercised	(186)		(186)
Shares issued from release of Restricted Stock Units	(3,636)	$ 2	(3,638)
Shares issued from release of Restricted Stock Units (in shares)		204
Repurchase of common stock	(8,464)					$ (8,464)
Repurchase of common stock (in shares)		(255)
Cash dividends declared on common stock, $0.30, $0.32, and $0.34 for the period ended June 30, 2015, December 31, 2015 and June 30, 2016, respectively	(14,820)			(14,820)
Common stock issued at $34.32 per share for stock bonus for the periods ended June 30, 2015 and December 31, 2015 and $32.45 June 30, 2016, respectively	552		552
Common stock issued (in shares)		16
Balance at Jun. 30, 2015	871,340	$ 493	229,279	665,914	(15,882)	(8,464)
Balance (in shares) at Jun. 30, 2015		49,121
Increase (Decrease) in Stockholders' Equity
Net income	36,328			36,328
Translation adjustment, net of tax	(12,237)				(12,237)
Pension adjustment, net of tax	(457)				(457)
Options exercised	4,144	$ 1	4,143
Stock options exercised (in shares)		141
Stock-based compensation	5,002		5,002
Tax benefit of options exercised	(132)		(132)
Shares issued from release of Restricted Stock Units	(80)	$ 0	(80)
Shares issued from release of Restricted Stock Units (in shares)		6
Repurchase of common stock	(38,680)					(38,680)
Repurchase of common stock (in shares)		(1,084)
Retirement of common stock	0	$ (13)		(47,131)		47,144
Cash dividends declared on common stock, $0.30, $0.32, and $0.34 for the period ended June 30, 2015, December 31, 2015 and June 30, 2016, respectively	(15,404)			(15,404)
Balance at Dec. 31, 2015	849,824	$ 481	238,212	639,707	(28,576)
Balance (in shares) at Dec. 31, 2015		48,184
Increase (Decrease) in Stockholders' Equity
Net income	42,544			42,544
Translation adjustment, net of tax	5,011				5,011
Options exercised	2,525	$ 1	2,524
Stock options exercised (in shares)		86
Stock-based compensation	5,951		5,951
Tax benefit of options exercised	19		19
Shares issued from release of Restricted Stock Units	(3,973)	$ 2	(3,975)
Shares issued from release of Restricted Stock Units (in shares)		215
Repurchase of common stock	(3,502)		0			(3,502)
Repurchase of common stock (in shares)		(106)
Cash dividends declared on common stock, $0.30, $0.32, and $0.34 for the period ended June 30, 2015, December 31, 2015 and June 30, 2016, respectively	(16,438)			(16,438)
Common stock issued at $34.32 per share for stock bonus for the periods ended June 30, 2015 and December 31, 2015 and $32.45 June 30, 2016, respectively	315		315
Common stock issued (in shares)		10
Balance at Jun. 30, 2016	$ 882,276	$ 484	$ 243,046	$ 665,813	$ (23,565)	$ (3,502)
Balance (in shares) at Jun. 30, 2016		48,389